Until now, there has been an air-conditioning apparatus executing a refrigeration cycle by using “hydrofluorocarbon (HFC) refrigerant” such as nonflammable R410A. The R410A is different from “hydrochlorofluorocarbon (HCFC) refrigerant” such as a conventional R22, zero in ozone depleting potential (ODP), never destroy the ozone layer, but high in global warming potential (hereinafter referred to as GWP). Therefore, a change of the HFC refrigerant such as the R410A high in GWP to refrigerant low in GWP (hereinafter referred to as low GWP refrigerant) has been made as one of global warming preventions.
There has been hydrocarbon (HC) refrigerant such as R290 (C3H8; propane) or R1270 (C3H6; propylene) being natural refrigerant as candidates for the low GWP refrigerant. Unlike the nonflammable R410A, the HC refrigerant is high in flammability, so that care and precaution must be taken not to leak refrigerant.
As candidates for the low GWP refrigerant, there has been the HFC refrigerant having no double bond of carbons in composition such as, for example, R32 (CH2H2; difluoro-methane) being lower in GWP than the R410A.
Furthermore, as a similar candidate for refrigerant, there has been halogenated hydrocarbon being one type of the HFC refrigerant similar to the R32 and having double bond of carbons in composition. As such halogenated hydrocarbon, there has been known, for example, HFO-1234yf (CF3CF═CH2; tetrafluoropropene) or HFO-1234ze (CF3—CH═CHF). The HFC refrigerant having double bond of carbons in composition is often represented as “HFO refrigerant” using “O” of olefin (because unsaturated hydrocarbon having double bond of carbons is called olefin) to discriminate from the HFC refrigerant having no double bond of carbons in composition, such as the R32.
The low GWP refrigerant such as the HFC refrigerant and the HFO refrigerant is not flammable than the HC refrigerant such as the R290 (C3H8; propane) being natural refrigerant, but slightly flammable unlike the nonflammable R410A. For this reason, care must be taken not to leak refrigerant, as is the case with the R290. Hereinafter, even the refrigerant that is slightly flammable is referred to as “flammable refrigerant.”
Patent Literature 1, for example, discusses a method of decreasing the risk of ignition caused in a case where the flammable refrigerant leaks by any chance, such that a refrigerant amount calculated from an installation floor space manually input according to a relational expression uniquely determined with reference to the following formula I related to an allowable refrigerant amount per room mmax [kg] being not ventilated and defined by International Electrotechnical Commission IEC60335-2-40 is compared with a refrigerant amount in an air-conditioning apparatus and the refrigerant exceeding the allowable refrigerant amount mmax is discharged and transferred to a surplus refrigerant storage unit.mmax=2.5×(LFL)1.25×h0×(A)0.5  (Formula I)mmax: Allowable refrigerant amount per room [kg]A: Installation floor space [m2]LFL: Lower flammability limit of refrigerant [kg/m3]h0: Installation height of unit (indoor unit) [m]Here, the installation height h0 is 0.6 m in a floor type, 1.8 m in wall type, 1.0 m in window type, and 2.2 m in ceiling type.